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Old 28th January 2006, 09:17 PM   #1
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Default anybody knows this ic????

Hallo I need information on this ic: 3 terminals voltage regulator used in my telefunken S900 to bring the voltage to 15volt DC, on the component is write NEC D288 L76 nearly '78; wich circuit I can use to improve the turntable psu ? I would like to change the little transformer with a bigger one external to the chassis and I will be happy to use the same circuit with better components but, I don't know if it is a variable regulator and this mean that my new transf. (output 24V) shouldn't be good to replace the older one, but if the ic is a fixed regualtor it should work fine ??? Any idea? It is a 78 component (the little circuit in my telefunken report the following character on the downside of the PCB: Lenco 40481 -21/sep/1978
Bye,
Domenico
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Old 28th January 2006, 09:42 PM   #2
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That sounds like a LM7815.
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Old 28th January 2006, 11:57 PM   #3
ilimzn is offline ilimzn  Croatia
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Nope, it sounds like a NEC 2SD288 55V 3A bipolar transistor... in a TO220 case, which is why kyrochan probably thought it was an IC regulator.
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Old 29th January 2006, 05:58 AM   #4
Nordic is offline Nordic  South Africa
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I find it pretty hard getting hold of NEC parts... spoke to a guy at RS last week who said they are adding tonnes of NEC stuff to their catalog later in the year...
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Old 29th January 2006, 08:20 AM   #5
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Many thanks, but this is used as regulator...this is the scheme that is used in the turntable psu any idea to improve it?
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Old 29th January 2006, 09:04 AM   #6
Eva is offline Eva  Spain
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It's definitely a 2SD288 NPN transistor used in a simple zener-regulated configuration.
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Old 29th January 2006, 11:07 AM   #7
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So have you got any idea to get better performances? If I change the 21volt transformer with a better 24V it should work, since the voltage is take from the "fixed" zener, right? Thanks to evrybody!
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Old 29th January 2006, 11:11 AM   #8
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Default 2SD288, and may have a zenner and a resistor around it

Also an output condenser to 15 volts...higher volt in the middle lead, the colector, and 15 volts to the base (the left lead)....the emitter may be 15.6 or 14.4, the rigth lead voltage, and those voltages will depends if the transistor is NPN or PNP.

As normal, Eva is rigth

regards,

Carlos
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Old 29th January 2006, 11:24 AM   #9
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Dear brazillian friend, so You suggest me to replace the caps with ones rated with higher volt value? I haven't understand the part on the zener diode, that depends on the tipology of the IC (npn or PNP) it is referred only on the leg wich they are connected, it is only an explain assert, right?
Do
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Old 29th January 2006, 11:27 AM   #10
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Default The transistor...NPN the damned.

Here it is Kirochan..... when transistor is NPN, or PNP, the zener polarity changes and also the electrolitic filter polarity changes...all voltages polarities change.

Normally we use NPN to positive voltages, of course you can do the opposite.

And is more common to use PNP to negative voltages, of course you can do also in the opposite way.

Image is not so clear as we want...but the maximum voltage from colector to emitter is around 55 Volts, and maximum current 3 amperes....i suppose you can change your supply without fear...if the input voltage changed too much...and to higher side...example:

Original was 24 volts
New supply will be 45 volts

This way, increasing the voltage, you will have more voltage from colector to emitter.... as power is the product of this voltage by the current will cross this transistor, power will increase and heat too...as you know, you will need to replace, or include a heatsink, if you already did not made that.

The explanation is around basic Knowledge, because this is the knowledge I HAVE, and not knowing if you are a doctor or a beginner, it is adequated to explain in the most simplest possible way...if you are a doctor, sorry by this stupid basic informations.

Someone, starting, learning, will find use with my explanation.

regards,

Carlos
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